This invention relates generally to mail article handling, and, more particularly to drop pocket door control.
Articles of mail currently are transported along a conveyor system with a plurality of drop pockets. Along the way the articles are sorted, identified, assigned, and oriented for a planned orderly placement in a specific drop pocket for distribution by the postal carrier. Sorting systems convey documents, such as mail, envelopes and the like, along a primary or main path from which the documents may be selectively diverted to a designated drop pocket or sorted according to predetermined criteria, such as a zip code as represented on a zip code label. An article will travel along the conveyor system until it reaches its designated drop pocket, at which time the drop pocket will open and the article is deposited within the drop pocket. The drop pocket will only open for those articles designated by a conveyor system controller for that specific drop pocket.
The objective of the conveyor system is to minimize the postal carriers"" effort in resorting and reorienting the mail articles after distribution. However, this orderly process is disrupted in the final stage when the articles are dropped from the conveyor system into the drop pocket at a level that inherently causes some articles to float into the drop pocket, thereby becoming disoriented requiring the postal carrier to reorient and possibly resort the mail. This added step by the postal carrier delays the start of the delivery process and may cause misdelivery of the article.
Buffering systems for stacking documents before being dropped into a receptacle or a bin are disclosed, for example, in U.S. Pat. Nos. 5,101,981; 5,503,388; and 5,538,140. These patents monitor the stack height or the quantity or the document thickness temporarily stored in a drop pocket at an elevation higher than the receptacle or the bin. U.S. Pat. Nos. 5,503,388, by Guenther et al, and 5,538,140, Guntherer et al, disclose mechanical and electronic devices that measure the current stack thickness. U.S. Pat. No. 5,101,981, by Carbone et al, monitors the quantity of documents fed to the buffer. U.S. Pat. No. 6,126,017, by Hours, measures the document thickness prior to entry on to the conveyor system, tracks stack height in the drop pocket, and opens the drop pocket bottom door and drops the contents of the drop pocket into a receptacle or bin disposed below when the stack in the drop pocket is nearly full.
It is a significant drawback where a system cannot determine actually whether the next document to be fed to the drop pocket will exceed the drop pocket height limit. To avoid possible system jams, these systems must limit the fed documents to a substantially known, constant thickness or the activation height of the measuring device must be no higher than the thickness document except in the sort run or drop a stack before the optimal height is reached. Limiting fed documents to those that are substantially the same thickness or dropping the stack before optimal height is reached may impact throughput and efficiency
The present invention provides a system that takes into consideration the individual thickness of substantially flat articles, preferably mail articles, stacked on top of other flat articles in order to determine the optimum thickness and number of flat articles that can be dropped together face down and still remain a unitary body during the drop. For the purposes of the present invention, a unitary body is defined as a stack of substantially flat articles oriented approximately on top of each other such that when the stack is dropped from a predetermined height the aerodynamic characteristics of the stack with a plurality of articles has substantially the same aerodynamic characteristics of a single article of the same height and weight. In other words, the present invention sortation and orientation system insures that the stack of flat articles do not separate when dropping into an output receptacle.
A computer, a thickness measurement device, and a conveyor implement the present invention. The present invention imports data from the thickness measurement device in order to ascertain the thickness of the next flat article. In addition thereto, the system of this invention counts the number of flat articles deposited on the top surface of the drop pocket door. By analyzing this information, a computer generates a signal to open the drop pocket that permits the dropping of a unitary body of substantially flat articles, when the total stack thickness and/or number of articles reaches threshold limits.